You admit a 61-year-old man to the intensive care unit after a witnessed generalized tonic-clonic seizure at home. He has a history of sarcoidosis and has been treated with prednisone 10 to 60 mg for the last year. Before admission, he had no cough or sputum production and had felt well. CT of the head, chest, abdomen, and pelvis reveals a 2.5 cm pulmonary nodule in the right upper lobe and 3 cm parenchymal brain lesion.
What is the MOST likely diagnosis?A. Pneumocystis jirovecii (formerly carinii) infection
Correct Answer: D
This case presentation is most consistent with nocardiosis, a classic “brain and lung” infectious syndrome (Answer D). Although nocardiosis typically presents in immune-compromised patients, up to one-third are immunocompetent. Infections caused by aerobic actinomycetes in the genus Nocardia are characterized by their ability to spread to any organ (especially the central nervous system) and a tendency to relapse or progress despite appropriate therapy. Glucocorticoids depress the phagocytic function of alveolar macrophages and neutrophils and alter antigen presentation and lymphocyte activation, increasing risk of bacterial and fungal infections. Virtually every chronic illness that requires prolonged glucocorticoid therapy has been associated with nocardiosis. P. jirovecii (formerly carinii) (Answer A) and sarcoidosis (Answer B) are not associated with parenchymal mass–like brain lesions. Although tuberculosis (Answer C) can present with masslike lesions in the brain parenchyma (tuberculomas), it is very uncommon to have simultaneously pulmonary and central nervous system tuberculomas/nodules. Furthermore, most patients with pulmonary tuberculosis present with cough.